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Population Growth and Resource Availability (3.5)

Size (N)

  • total # of individuals  in a given area at a given time

  • larger size (N)

  • safer from population decline

Density

  • number of individuals/area

    • Higher density

      • higher competition, possibility for disease outbreak, possibility of depleting food source

Distribution

  • how individuals in a population are spaced out compared to each other

    • random: trees

    • uniform: territorial animals

    • clumped: herd/group animals

Sex Ratio

  • ratio of males to females

    • closer to 50:50 ideal for breeding

    • die off or bottleneck effect can lead to to skewed sex ratio (not enough females) limiting pop. growth

Density-Dependent-Factors

  • factors that influence population growth based on size

  • Examples

    • food

    • light

    • competition for habitat

    • water

    • disease

  • All these things limit population growth based on their size

Density-Independent Factors

  • factors that influence population growth independence of their size.

  • examples

    • natural disasters

    • floods

    • hurricane tornado

    • fire

  • It doesn’t matter how big or small a pop. is, natural disasters limit them both

Ex. of Density-Dependent Factor

  • Food is a density dependent factor. (also a limiting resource)

  • When twice as much food was added to the dish, both species increased carrying capacity by about 2x

  • Biotic Potential

  • Max potential growth rate with no limiting resources

  • May occur initially, but limiting resources (competition, food, disease, predators) slow growth, & eventually limit pop. to carrying capacity (k)

Biotic potential

  • exponential growth

Logistic growth

  • initial rapid growth, then limiting factors limit pop. to K


Population Growth and Resource Availability (3.5)

Size (N)

  • total # of individuals  in a given area at a given time

  • larger size (N)

  • safer from population decline

Density

  • number of individuals/area

    • Higher density

      • higher competition, possibility for disease outbreak, possibility of depleting food source

Distribution

  • how individuals in a population are spaced out compared to each other

    • random: trees

    • uniform: territorial animals

    • clumped: herd/group animals

Sex Ratio

  • ratio of males to females

    • closer to 50:50 ideal for breeding

    • die off or bottleneck effect can lead to to skewed sex ratio (not enough females) limiting pop. growth

Density-Dependent-Factors

  • factors that influence population growth based on size

  • Examples

    • food

    • light

    • competition for habitat

    • water

    • disease

  • All these things limit population growth based on their size

Density-Independent Factors

  • factors that influence population growth independence of their size.

  • examples

    • natural disasters

    • floods

    • hurricane tornado

    • fire

  • It doesn’t matter how big or small a pop. is, natural disasters limit them both

Ex. of Density-Dependent Factor

  • Food is a density dependent factor. (also a limiting resource)

  • When twice as much food was added to the dish, both species increased carrying capacity by about 2x

  • Biotic Potential

  • Max potential growth rate with no limiting resources

  • May occur initially, but limiting resources (competition, food, disease, predators) slow growth, & eventually limit pop. to carrying capacity (k)

Biotic potential

  • exponential growth

Logistic growth

  • initial rapid growth, then limiting factors limit pop. to K


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